1. Field of the Invention
The present invention relates to a method for driving a tracking element and a driving device using the same. More particularly, the present invention relates to a method for adaptively driving a tracking element with mechanical deviation and a driving device using the same.
2. Description of Related Art
FIG. 1A is a view of a driving mechanism of a conventional optical disc drive. The mechanism of the optical disc drive includes a transmission bar 101, an optical head 102, a mirror mount 103, a tracking gear set 104, and a sledge tracking motor 105. The sledge tracking motor 105 pushes the optical head 102 to move along the transmission bars 101 through the tracking gear set 104. The mirror mount 103 is disposed on the optical head 102 for focusing the light beams emitted from inside the optical head 102 to access data. FIG. 1B is a motion graph of the driving mechanism of a conventional optical disc drive. In general, as the optical disc 107 has a large number of tracks, dual stoppers are usually used to reduce the moving time of the optical head 102 to the position to be read. First, the optical head 102 is forced to move a longer distance, for example, across hundreds of tracks, by the sledge tracking motor 105. Next, the mirror mount 103 is forced to move a shorter distance, for example, less than a track, by the stopper 106 inside the optical head, so as to reduce the reading time and improve the precision by division of work.
Referring to FIGS. 1A and 1B, in order to move the mirror mount 103 to the position SD to read the data in the optical disc 107, generally the optical head 102 is forced to move from the position SA to SB by the sledge tracking motor 105. Next, the mirror mount 103 is forced to move from the position SC to SD by the stopper 106 inside the optical head. In general, the principle of the motion mechanism of the optical disc drive is to supply the voltage to the sledge tracking motor 105. When the sledge tracking motor 105 is initiated, the tracking gear set 104 is driven to bring the optical head 102 gliding on the transmission bars 101. Therefore, the optical head 102 is forced to move a long distance, for example, across hundreds of tracks. Next, the stopper 106 inside the optical head (usually a voice coil motor) pushes the mirror mount 103 moving a short distance according to the principle of electromagnetic induction, so as to track more precisely.
When the optical head 102 is moving, in order to make the optical head 102 reach the predetermined position, track crossing signals on the optical disc 107 are detected (i.e., using the radio frequency (RF) and the tracking error (TE) signals for mutual determination) for correcting the position and speed. However, when the friction changes, for example, the friction increases due to the bad engagement of the gear set, the open loop cannot compensate completely. Therefore, the optical disc drive adopting such a gear set is regarded as unqualified.